Anthracene based selective Co (II) colorimetric and fluorescent sensor for cytotoxicity studies and real sample analysis

A novel and highly selective fluorescent optical sensor developed from 9-anthracene carboxaldehyde and 2-amino 5-nitro benzophenone (BPAI) was designed and synthesized by ultrasonication for rapid Co2+ detection in ethanol medium by charge transfer and CHEF (Chelation Enhanced Fluorescence) mechanism. The stoichiometry of the complexation was calculated as 1:1 via Job's plot and confirmed by mass spectrum. The structure of both the ligand and the metal complex was confirmed by UV, FT-IR, NMR and mass spectral studies. The mechanism of sensing was observed through experimental calculations. Upon treatment of various metal cations such as Cu2+, Ni2+, Zn2+, Cr3+, Mg2+, Hg2+, Fe2+, Fe3+, Cd2+, Pb2+,Al3+, Pd2+, K+, Na+,As3+ no noticeable changes were observed in both absorbance and fluorescence spectral measurements except that of Co2+. The absorbance of BPAI + Co2+ exhibited two new peaks at 616 nm and 679 nm. The fluorescence response of BPAI at 580 nm was abruptly increased, accompanied by the colour change of the BPAI with Co2+ compared to BPAI. The color change from pale brown to yellow occurred due to the binding of Co2+ with that of BPAI thereby yielding a fluorescence-enhanced product. BPAI exhibited significant selectivity within short response time and strong charge transfer mechanism due to the chelation process. The detection limit was found to be 0.00091 μM which is much lower than the permissible limit recommended by WHO. Real sample analysis was performed for the practical applicability of BPAI in the environment. Furthermore, BPAI can be used as a colorimetric and fluorescent sensor to detect Co2+ in biological environments, demonstrating its low cytotoxicity using MTT assay by MG63 cells and L929 cells.